At present, an inkjet print head more widely used is a piezoelectric inkjet print head. A spray head of a general piezoelectric inkjet print head is a piezoelectric device, and each nozzle of the spray head is driven by a piece of piezoelectric ceramic wafer. When an excitation pulse voltage is applied to a corresponding piezoelectric ceramic wafer at a controlled slew rate, the piezoelectric ceramic wafer is excited to offset outwards to form a negative pressure wave, thereby absorbing ink into a cavity. After a fixed pulse lasts a period of time, the excitation pulse voltage is removed at a certain controlled slew rate. In this way, with relaxation and contraction of walls of the cavity, an overall positive pressure wave is made to propagate forwards to cause the nozzles to jet ink, thereby achieving inkjet printing.
Wherein the excitation pulse applied to an execution element of the piezoelectric ceramic wafer to drive it to deform is generally generated by a dedicated high-voltage pulse generating device. FIG. 1 shows a structure of a typical high-voltage pulse generating device for generating trapezoidal pulses, in which a low-voltage pulse generator generates a low-voltage excitation pulse required according to a front-end synchronization pulse, a subsequent controlled gain amplifier adjusts amplitude gain of the low-voltage excitation pulse, and finally a linear high-voltage power amplifier outputs a high-voltage excitation pulse required.
The synchronization pulse input from the front end of the high-voltage pulse generating device as shown in FIG. 1 temporally controls the high-voltage excitation pulse finally output, and a corresponding relationship between waveforms of the two pulses is shown in FIG. 2, in which a lateral axis represents time, and a longitudinal axis represents voltage. It can be seen from FIG. 2 that the width (duration) of the synchronization pulse decides the duration of the high-voltage excitation pulse finally output, and an inappropriate width of the synchronization pulse will directly affect the output of the high-voltage excitation pulse and the normal operation of the spray head.
FIG. 3 shows an output waveform of the resultant corresponding high-voltage excitation pulse generated when the width of the synchronization pulse is too short. It can be seen that the output high-voltage excitation pulse assumes a waveform in a spike pulse form, and this high-voltage spike pulse, on one hand, can not drive the spray head to generate appropriate ink droplets and affects the lifetime of the spray head, and on the other hand, brings damage to the high-voltage pulse generating device itself. FIG. 4 shows an output waveform of the resultant corresponding high-voltage excitation pulse generated when the width of the synchronization pulse is too long. It can be seen that the duration of the high-voltage excitation pulse output is too long, and a high voltage is maintained for a long time on the spray head, which can not drive the spray head to generate appropriate ink droplets as well and would lead to fatigue of the spray head.